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Abstract:

An exhaust port structure of a cylinder head includes a connection pipe
communicating with a plurality of exhaust ports of the cylinder head and
an exhaust hole connected to the connection pipe and performing a
function of an exhaust manifold, wherein the connection pipe has an EGR
line integrally formed and connected thereto and each of the exhaust
ports is formed with the same shape or a symmetrical shape, and the
present invention can reduce the weight of the cylinder head and the
manufacturing cost and improve the EGR rate and T/C efficiency.

Claims:

1. An exhaust port structure of a cylinder head comprising: a connection
pipe communicating with a plurality of exhaust ports of the cylinder
head; and an exhaust hole connected to the connection pipe and performing
a function of an exhaust manifold; wherein the connection pipe has an EGR
line integrally formed and connected thereto, and each of the exhaust
ports is formed with the same shape or a symmetrical shape.

2. The exhaust port structure of claim 1, wherein the exhaust hole is
formed at a position corresponding to an inlet of a turbocharger.

3. The exhaust port structure of claim 2, wherein the EGR line is
extended from a side surface of the connection pipe where the exhaust
hole is formed.

4. The exhaust port structure of claim 1, wherein outlets of the exhaust
ports are located apart from each other by a predetermined distance.

5. The exhaust port structure of claim 1, wherein the connection pipe is
a cuboid pipe having a predetermined width and height.

6. The exhaust port structure of claim 1 which is applied to a diesel
engine.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority of Korean Patent
Application Number 10-2011-0102580 filed Oct. 7, 2011, the entire
contents of which application is incorporated herein for all purposes by
this reference.

BACKGROUND OF INVENTION

[0002] 1. Field of Invention

[0003] The present invention relates to an exhaust port structure of a
cylinder head. More particularly, the present invention relates to an
exhaust port structure of a cylinder head in which an exhaust manifold is
integrally formed to the cylinder head so as to reduce weight and improve
efficiency.

[0004] 2. Description of Related Art

[0005] In the case of a diesel engine, an exhaust system may include a
cylinder head having a plurality of exhaust ports, an exhaust manifold,
and a turbocharger.

[0006] In most cases, the exhaust manifold is made from expensive
materials such as steel use stainless SUS, and the weight of the exhaust
manifold is over 3 kg. Therefore, an exhaust manifold integrated cylinder
head in which the exhaust manifold is integrally formed with the exhaust
ports is provided so as to reduce the weight of the cylinder head and
improve durability.

[0007] FIG. 1 is a schematic drawing of a conventional art in which the
exhaust manifold is integrally formed with the exhaust ports. As shown in
FIG. 1, the conventional art has a problem in that there is a large
deviation in the flow coefficients Cf of the exhaust ports because the
shape of the exhaust ports 1 and 4 connected to the first cylinder C1 and
the fourth cylinder C4 is different from the shape of the exhaust ports 2
and 3 connected to the second cylinder C2 and the third cylinder C3. The
flow coefficient Cf is defined as a ratio of a quantity of exhaust gas
flowing from a combustion chamber after combustion to a quantity of
exhaust gas flowing from the end of an exhaust pipe. A smaller deviation
of the exhaust flow coefficient of Cf is better for the exhaust gas
recirculation rate (EGR rate) and the turbocharger efficiency (T/C
efficiency). However, the deviation is large in the case of the
conventional art because the flowing routes of the exhaust ports are
different from each other because of the shape and length difference of
the exhaust ports, such that the prior art has a problem of deteriorating
the exhaust gas recirculation rate (EGR rate) and the turbocharger
efficiency (T/C efficiency).

[0008] Further, the conventional art has a problem that the probability of
a head crack increases significantly when the heat load is increased
because of the exhaust gas, since the outlets of the exhaust ports 1, 2,
3, and 4 are so close to each other to make up a bulkhead structure S as
shown in FIG. 1.

[0009] The structure of the conventional art shown in FIG. 1 is also
difficult to apply to a diesel engine which is provided with a
turbocharger because an exhaust hole 5 is located between the second
cylinder C2 and the third cylinder C3.

[0010] In the case of the diesel engine provided with a turbocharger, the
turbocharger can be located between the third cylinder C3 and the fourth
cylinder C4 because it is more profitable for the diesel engine
considering lay-out of the diesel engine and load capacity of the
vehicle. But in the case of the conventional art, the exhaust hole 5 is
located between the second cylinder C2 and the third cylinder C3 as shown
in FIG. 1 such that it is structurally difficult to connect the
turbocharger with the exhaust hole 5.

[0011] The information disclosed in this Background section is only for
enhancement of understanding of the general background of the invention
and should not be taken as an acknowledgement or any form of suggestion
that this information forms the prior art already known to a person
skilled in the art.

SUMMARY OF INVENTION

[0012] Various aspects of the present invention provide for an exhaust
port structure of a cylinder head having advantages of reducing weight,
improving the EGR rate and the T/C efficiency, and decreasing the
probability of a head crack.

[0013] Various aspects of the present invention provide for an exhaust
port structure of a cylinder head that may include a connection pipe
communicating with a plurality of exhaust ports of the cylinder head and
an exhaust hole connected to the connection pipe and performing a
function of an exhaust manifold, wherein the connection pipe has an EGR
line integrally formed and connected thereto, and each of the exhaust
ports is formed with the same shape or a symmetrical shape.

[0014] The exhaust hole may be formed at a position corresponding to an
inlet of a turbocharger.

[0015] The EGR line may be extended from a side surface of the connection
pipe where the exhaust hole is formed.

[0016] Outlets of the exhaust ports are located apart from each other by a
predetermined distance.

[0017] The connection pipe may be a cuboid pipe having a predetermined
width and height.

[0018] The exhaust port structure may be applied to a diesel engine.

[0019] The exhaust ports of the cylinder head may be integrally formed
with the exhaust manifold and further integrally formed with an EGR line
such that the weight of the cylinder head can be reduced by deleting an
extra pipe for the EGR line.

[0020] Various aspects of the present invention provide for improving the
EGR rate and the T/C efficiency since each of the exhaust ports is formed
with the same shape or a symmetrical shape with reference to the exhaust
hole. Various aspects of the present invention provide for an effect that
can prevent occurrence of a head crack by disposing each of the exhaust
ports apart from each other by a predetermined distance.

[0021] The methods and apparatuses of the present invention have other
features and advantages which will be apparent from or are set forth in
more detail in the accompanying drawings, which are incorporated herein,
and the following Detailed Description, which together serve to explain
certain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 is a drawing of an exhaust port structure of a cylinder head
according to the conventional art.

[0023]FIG. 2 is a drawing of an exhaust port structure of an exemplary
cylinder head according to the present invention.

[0024] FIG. 3 is a perspective view of an exhaust port structure of an
exemplary cylinder head according to the present invention.

[0025]FIG. 4 is a cross-sectional view of an exemplary exhaust port
according to the present invention.

[0026] FIG. 5 is a cross-sectional view of an exhaust port structure of an
exemplary cylinder head according to the present invention.

DETAILED DESCRIPTION

[0027] Reference will now be made in detail to various embodiments of the
present invention(s), examples of which are illustrated in the
accompanying drawings and described below. While the invention(s) will be
described in conjunction with exemplary embodiments, it will be
understood that present description is not intended to limit the
invention(s) to those exemplary embodiments. On the contrary, the
invention(s) is/are intended to cover not only the exemplary embodiments,
but also various alternatives, modifications, equivalents and other
embodiments, which may be included within the spirit and scope of the
invention as defined by the appended claims.

[0028] As shown in FIG. 2 to FIG. 5, the exhaust port structure of a
cylinder head according to various embodiments of the present invention
is integrally provided with a connection pipe 20 which communicates with
a plurality of exhaust ports 11, 12, 13, and 14 of the cylinder so as to
perform a function of an exhaust manifold, and the connection pipe 20 has
an EGR line 30 integrally and/or monolithically formed and connected
thereto. In the present invention, the exhaust ports 11, 12, 13, and 14
of the cylinder head are integrally and/or monolithically formed with the
exhaust manifold and the EGR line 30 such that the weight of the cylinder
head can be reduced by eliminating an extra pipe for the EGR line 30.

[0029] It is represented by actual experiments and analysis of applying
the present invention to a diesel engine of a car that the weight of the
car can be reduced by about 1.74 kg and the cost can be reduced by over
47,000 won by omitting the exhaust manifold and reducing manufacturing
processes for the cylinder head.

[0030] Each of the exhaust ports 11, 12, 13, and 14 is divided into two
ports 11a and 11b, 12a and 12b, 13a and 13b, and 14a and 14b, and the two
divided ports 11a and 11b, 12a and 12b, 13a and 13b, and 14a and 14b are
combined into one outlet 11c, 12c, 13c, and 14c at the region where the
connection pipe 20 communicates with the exhaust ports 11, 12, 13, and
14. The exhaust ports 11, 12, 13, and 14 are gradually curved around to
an exhaust hole 40. For this, as shown in FIG. 2, one part 11b, 12b, 13b,
and 14a of the two divided ports may be formed as a straight passage,
while the other part 11a, 12a, 13a, and 14b may be formed as a curved
passage which is curved around to the exhaust hole 40.

[0031] Each of the exhaust ports 11, 12, 13, and 14 may be formed with the
same shape or a symmetrical shape. As shown in FIG. 2, each of the
exhaust ports 11, 12, and 13 which communicate with the first, second,
and third cylinders C1, C2, and C3 may be formed with the same shape, and
the exhaust port 14 which communicates with the fourth cylinder C4 may be
formed with a shape that is symmetrical to the shape of the exhaust ports
11, 12, and 13. The exhaust port 14 communicating with the fourth
cylinder C4 is bent in the opposite direction in comparison with the
exhaust ports 11, 12, and 13 communicating with the first, second, and
third cylinders C1, C2, and C3 because the exhaust hole 40 is located
between the third cylinder C3 and the fourth cylinder C4.

[0032] The above-mentioned same shape or symmetrical shape of the exhaust
ports 11, 12, 13, and 14 has an effect of lowering the deviation of the
flow coefficient.

[0033] The reason for forming the exhaust ports 11, 12, 13, and 14 with
the same shape or a symmetrical shape is to improve the exhaust gas
recirculation rate (EGR rate) and turbocharger efficiency (T/C
efficiency). The actual flow paths through the exhaust ports 11, 12, 13,
and 14 become the same by making the exhaust port 14 which is in the
opposite direction to the exhaust ports 11, 12, and 13 with reference to
the exhaust hole 40 symmetrical in comparison with the shape of the
exhaust ports 11, 12, and 13. Therefore the deviation of the flow
coefficient (Cf) of each of the exhaust ports 11, 12, 13, and 14 becomes
smaller.

[0034] As aforementioned, the flow coefficient Cf is defined as a ratio of
a quantity of exhaust gas flowing from a combustion chamber after
combustion to a quantity of exhaust gas flowing from the end of an
exhaust hole 40. A smaller deviation of the exhaust flow coefficient (CO
is better for the EGR rate and T/C efficiency, and a larger the flow
coefficient (CO is better for an aspect of back pressure.

[0035] Each outlet of the exhaust ports 11c, 12c, 13c, and 14c is located
at the connection pipe 20 apart from each other by a predetermined
distance. In various embodiments, as shown in FIG. 2, each outlet of the
exhaust ports 11c, 12c, 13c, and 14c may be located apart from each other
by a size of the outlet for preventing the bulkhead structure.

[0036] In comparison with the conventional art shown in FIG. 1, the
conventional art has a problem of increasing head cracks because the
outlets of the exhaust ports 1, 2, 3, and 4 are so close to make up a
bulkhead structure S between the cylinders C1, C2, C3, and C4 such that
the probability of head crack increases when the heat load is increased
by exhaust gas. But the present invention, as shown in FIG. 2, has a
structure that does not make up a bulkhead structure between the
cylinders C1, C2, C3, and C4 and can disperse a heat load of exhaust gas
by arranging each outlet of the exhaust ports 1, 2, 3, and 4 apart from
each other by a predetermined distance. Therefore the present invention
can significantly lower the probability of head cracks in comparison with
the conventional art.

[0037] In various embodiments, as shown in FIG. 2, the connection pipe 20
may be a cuboid pipe having a predetermined width D and height C. The
width D and the height C of the connection pipe 20 can be determined
diversely according to the size, the structure, etc., of the exhaust
port. In experiments with diesel engine cars, it was shown that the flow
coefficient Cf and the T/C efficiency could be improved by forming the
height C of the connection pipe 20 in the range of 23 to 25 mm and the
width D of the connection pipe 20 in the range of 38 to 42 mm.

[0038] In the exhaust port structure of a cylinder head according to the
present invention, the exhaust hole 40 may be formed at a position
corresponding to an inlet of a turbocharger.

[0039] It is profitable for a diesel engine vehicle with a turbocharger to
locate the turbocharger between the third cylinder C3 and the fourth
cylinder C4 of the diesel engine shown in FIG. 2 considering the lay-out
of the diesel engine and the load capacity of the vehicle. The present
invention can be effectively adapted to the diesel engine by forming the
exhaust hole 40 at a position corresponding to an inlet of a turbocharger
considering the structure of the diesel engine with a turbocharger.

[0040] As shown in FIG. 2 to FIG. 5, the EGR line 30 can also be extended
along to a side where the exhaust hole 40 is positioned by considering
the above-mentioned position of the exhaust hole 40. This is because
forming the EGR line 30 near the exhaust hole 40 is advantageous for
exhaust gas recirculation.

[0041] The optimum structure of the exhaust port structure of the cylinder
head according to the present invention can be determined by using the
technique of design for six sigma (DFSS). DFSS is a business-process
management methodology related to traditional six sigma, and six sigma is
a business management strategy, originally developed by Motorola USA, in
1986, and today it is widely used in many sectors of industry. Six sigma
seeks to improve the quality of process outputs by identifying and
removing the causes of defects (errors) and minimizing variability in
manufacturing and business processes. The optimum structure can be
determined by selecting the radius of curvature of the bending portion
(A) formed by bending down the exhaust ports 11, 12, 13, and 14 shown in
FIG. 3 to FIG. 4, the length of the divided part (B) of each of the
exhaust ports 11, 12, 13, and 14, and the height (C) and the width (D) of
the connection pipe 20 as control parameters, selecting the deviation of
the cylinders C1, C2, C3, and C4 as noise parameter, and using flow
analysis.

[0042] In experiments, 35 mm is selected as the optimum radius of
curvature (R) of the bending portion (A) of the exhaust ports 11, 12, 13,
and 14 in the range of 35 to 45 mm, 48 mm is selected as the optimum
length (B) of the divided parts of the exhaust ports 11, 12, 13, and 14
in the range of 45 to 51 mm, 25 mm is selected as the optimum height (C)
of the connection pipe 20 in the range of 23 to 25 mm, and 42 mm is
selected as the optimum width (D) of the connection pipe 20 in the range
of 38 to 42 mm.

[0043] The results of testing and analysis with respect to the exhaust
port structure of a cylinder head applying the above-mentioned optimum
radius of curvature (R), optimum length (B), optimum height (C), and
optimum width (D) show that the flow coefficient (Cf) of the exhaust port
is improved by over 5.1% and the deviation of the cylinder is improved by
about 38% in comparison with the conventional art.

[0044] For convenience in explanation and accurate definition in the
appended claims, the terms upper or lower, front or rear, inside or
outside, and etc. are used to describe features of the exemplary
embodiments with reference to the positions of such features as displayed
in the figures.

[0045] The foregoing descriptions of specific exemplary embodiments of the
present invention have been presented for purposes of illustration and
description. They are not intended to be exhaustive or to limit the
invention to the precise forms disclosed, and obviously many
modifications and variations are possible in light of the above
teachings. The exemplary embodiments were chosen and described in order
to explain certain principles of the invention and their practical
application, to thereby enable others skilled in the art to make and
utilize various exemplary embodiments of the present invention, as well
as various alternatives and modifications thereof. It is intended that
the scope of the invention be defined by the Claims appended hereto and
their equivalents.